High powered lasers used for welding or drilling are well known in the art. Typically, these lasers, such as the high powered (14 kilowatt) CW laser marketed by the Industrial Laser Division of United Technologies Corporation, are of the transverse electrode convective flow type. In these lasers, a gaseous lasing medium are flowed through a region of opposed electrodes. A gas discharge is created between the electrodes, creating the population inversion that is needed to generate a high powered, coherent discharge.
While these high powered convective flow lasers may have a variety of optical configurations, many of the most successful ones marketed currently are characterized by a confocal unstable resonator optical geometry. This resonator geometry is characterized by an output beam whose beam profile is, in theory, annular. However, the known lasers of the above type are characterized by an asymmetry in the beam profile produced as a result of an index change in the gas. The high powers associated with these devices create a region usually near the cathode which is at a substantially higher temperature than that of the remainder of the lasing medium. The higher temperature region is characterized by a different index of refraction, yielding an output beam with a truncated profile. Efforts to correct for this phenomenon have centered on trying to minimize or eliminate the region of higher temperature and have met with limited success.
It would be advantageous to have a high powered laser of the aforementioned type characterized by a symmetric output beam profile. The present invention is drawn towards such a laser.